This invention relates to a fuel and pressure gas supply system for an internal combustion engine having a gas pressure operated fuel metering and/or injecting apparatus. There are a number of internal combustion engines which use air under pressure in association with the admission of the fuel supply to the engine. One fuel metering system using air pressure as a means of delivery of the fuel is disclosed in the Applicant's co-pending application Ser. No. 532,035, based on Australian Patent Application No. PF2123/81.
The majority of fuel supply systems of the above type the fuel is drawn from the fuel tank through the fuel metering system and the excess fuel returned to the tank. It is also common for air to become entrained in the fuel returned to the tank and thus a mixture of fuel and fuel vapour is returned to the tank. Also in some of the air pressure operated fuel systems, such as the one referred to in the above co-pending application, there is air exhausted from the system, and under current pollution requirements, such air cannot be exhausted directly into the atmosphere.